1. Field of the Invention
The present invention relates to an image forming apparatus such as a copying machine, a printer, or the like using an electrophotography method or an electrostatic recording method.
2. Description of the Related Art
To make it possible for an image forming apparatus to handle a wide variety of types of recording materials, it is known to provide a transfer portion therein that transfers a toner image formed on a photosensitive drum or the like functioning as an image bearing member to an intermediate transfer member and further transfers the toner image from the intermediate transfer member to a recording material.
Japanese Patent Laid-Open No. 2004-29054 discloses a technique in which a transfer portion for transferring a toner image to a recording material is configured such that it has a large width in a direction in which the recording material is conveyed to thereby reduce an applied voltage and achieve an improvement in image quality. More specifically, the transfer portion includes two inner transfer rollers located in contact with an inner surface of an intermediate transfer member and two outer transfer rollers that are located in contact with an outer surface of the intermediate transfer member and that are urged against the respective two inner transfer rollers via the intermediate transfer member. In this technique disclosed in Japanese Patent Laid-Open No. 2004-29054, a transfer electric field is set such that it has a maximum value at the location of the downstream inner transfer roller.
Japanese Patent Laid-Open No. 2010-243553 discloses a technique in which a roller and a plate are used to transfer a toner image from a transfer belt to a recording material. In this technique disclosed in Japanese Patent Laid-Open No. 2010-243553, to enhance a transfer efficiency, a current flowing through the plate disposed at a downstream location is set to be lower than a current flowing through the roller disposed at an upstream location.
However, if the moisture content of the recording material is low, then this can produce a problem that the recording material becomes electrostatically stuck to the intermediate transfer member and the recording material remains on the intermediate transfer member without being separated from the intermediate transfer member after the transfer is complete.